1. A Franz Joseph dreadnought (teased in episode 1),
Very unlikely, given the history animosity between the FJ estate and Paramount Global, but the teaser suggests it's possible.
2. An Ambassador class, or any kinds of variants thereof,
A solid choice.
3. Some original fan-made older designs,
Not going to happen unfortunately, too much of a legal minefield
4. FASA designs,
Unlikely for similar reasons, but arrangements have IIRC been made in the past, so...
5. A Huron-type TAS freighter,
Hard to see why such a craft would warrant a place in the museum, but there are no legal issues.
6. And of course the Enterprise-D saucer.
All good with me.